Colorectal Cancer (CRC) is among the leading causes of morbidity. The chance of surviving CRC is closely related to the stage of the disease at diagnosis; the earlier the diagnosis, the greater the likelihood of survival. In many instances CRC is preceded by colorectal polyps, particularly adenomatous colorectal polyps. If identified early at the colorectal polyp or precancerous lesion stage, CRC is more likely to be curable. Therefore, subjects with CRC and/or colorectal polyps would greatly benefit from early diagnosis.
Current CRC screening methods consist of one or a combination of the followings: fecal occult blood testing (FOBT), flexible sigmoidoscopy, air-contrast barium enema, computerized tomography colonography (CTC) and/or colonoscopy. These current screening methods all have limitations or potential risks that limit their application.
Colonoscopy is currently the standard test for the presence or absence of CRC or colorectal polyps. However, colonoscopy is invasive and can impose unnecessary hazards and risks caused by sedation or the procedure itself. A known non-invasive CRC diagnostic method is FOBT. FOBT, however, has very low sensitivity in detection of CRC and is unattractive as the handling of fecal matter is required. CTC is a recent non-invasive technique for imaging the colon. However, its performance varies due primarily to technological differences in the subject preparation and the hardware and software used for the analysis. Several new screening methods based on DNA analysis are now available. These are typically PCR-based assays used to identify mutations known to occur in the adenoma-to-carcinoma sequence, or in familial CRC. However, whether genomics-based tests will result in high diagnostic accuracy for sporadic CRC remains to be seen.
Accordingly, there is a need to develop improved methods of assessing CRC and colorectal polyps in a subject.